// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef MEDIA_FILTERS_DECRYPTING_DEMUXER_STREAM_H_
#define MEDIA_FILTERS_DECRYPTING_DEMUXER_STREAM_H_

#include "base/callback.h"
#include "base/macros.h"
#include "base/memory/ref_counted.h"
#include "base/memory/weak_ptr.h"
#include "media/base/audio_decoder_config.h"
#include "media/base/cdm_context.h"
#include "media/base/decryptor.h"
#include "media/base/demuxer_stream.h"
#include "media/base/pipeline_status.h"
#include "media/base/video_decoder_config.h"

namespace base {
class SingleThreadTaskRunner;
}

namespace media {

class DecoderBuffer;
class MediaLog;

// Decryptor-based DemuxerStream implementation that converts a potentially
// encrypted demuxer stream to a clear demuxer stream.
// All public APIs and callbacks are trampolined to the |task_runner_| so
// that no locks are required for thread safety.
class MEDIA_EXPORT DecryptingDemuxerStream : public DemuxerStream {
public:
    DecryptingDemuxerStream(
        const scoped_refptr<base::SingleThreadTaskRunner>& task_runner,
        const scoped_refptr<MediaLog>& media_log,
        const base::Closure& waiting_for_decryption_key_cb);

    // Cancels all pending operations immediately and fires all pending callbacks.
    ~DecryptingDemuxerStream() override;

    // |steram| must be encrypted and |cdm_context| must be non-null.
    void Initialize(DemuxerStream* stream,
        CdmContext* cdm_context,
        const PipelineStatusCB& status_cb);

    // Cancels all pending operations and fires all pending callbacks. If in
    // kPendingDemuxerRead or kPendingDecrypt state, waits for the pending
    // operation to finish before satisfying |closure|. Sets the state to
    // kUninitialized if |this| hasn't been initialized, or to kIdle otherwise.
    void Reset(const base::Closure& closure);

    // Returns the name of this class for logging purpose.
    std::string GetDisplayName() const;

    // DemuxerStream implementation.
    void Read(const ReadCB& read_cb) override;
    AudioDecoderConfig audio_decoder_config() override;
    VideoDecoderConfig video_decoder_config() override;
    Type type() const override;
    Liveness liveness() const override;
    void EnableBitstreamConverter() override;
    bool SupportsConfigChanges() override;
    VideoRotation video_rotation() override;
    bool enabled() const override;
    void set_enabled(bool enabled, base::TimeDelta timestamp) override;
    void SetStreamStatusChangeCB(const StreamStatusChangeCB& cb) override;

private:
    // For a detailed state diagram please see this link: http://goo.gl/8jAok
    // TODO(xhwang): Add a ASCII state diagram in this file after this class
    // stabilizes.
    // TODO(xhwang): Update this diagram for DecryptingDemuxerStream.
    enum State {
        kUninitialized = 0,
        kIdle,
        kPendingDemuxerRead,
        kPendingDecrypt,
        kWaitingForKey
    };

    // Callback for DemuxerStream::Read().
    void DecryptBuffer(DemuxerStream::Status status,
        const scoped_refptr<DecoderBuffer>& buffer);

    void DecryptPendingBuffer();

    // Callback for Decryptor::Decrypt().
    void DeliverBuffer(Decryptor::Status status,
        const scoped_refptr<DecoderBuffer>& decrypted_buffer);

    // Callback for the |decryptor_| to notify this object that a new key has been
    // added.
    void OnKeyAdded();

    // Resets decoder and calls |reset_cb_|.
    void DoReset();

    // Returns Decryptor::StreamType converted from |stream_type_|.
    Decryptor::StreamType GetDecryptorStreamType() const;

    // Creates and initializes either |audio_config_| or |video_config_| based on
    // |demuxer_stream_|.
    void InitializeDecoderConfig();

    scoped_refptr<base::SingleThreadTaskRunner> task_runner_;

    scoped_refptr<MediaLog> media_log_;

    State state_;

    PipelineStatusCB init_cb_;
    ReadCB read_cb_;
    base::Closure reset_cb_;
    base::Closure waiting_for_decryption_key_cb_;

    // Pointer to the input demuxer stream that will feed us encrypted buffers.
    DemuxerStream* demuxer_stream_;

    AudioDecoderConfig audio_config_;
    VideoDecoderConfig video_config_;

    Decryptor* decryptor_;

    // The buffer returned by the demuxer that needs to be decrypted.
    scoped_refptr<media::DecoderBuffer> pending_buffer_to_decrypt_;

    // Indicates the situation where new key is added during pending decryption
    // (in other words, this variable can only be set in state kPendingDecrypt).
    // If this variable is true and kNoKey is returned then we need to try
    // decrypting again in case the newly added key is the correct decryption key.
    bool key_added_while_decrypt_pending_;

    base::WeakPtr<DecryptingDemuxerStream> weak_this_;
    base::WeakPtrFactory<DecryptingDemuxerStream> weak_factory_;

    DISALLOW_COPY_AND_ASSIGN(DecryptingDemuxerStream);
};

} // namespace media

#endif // MEDIA_FILTERS_DECRYPTING_DEMUXER_STREAM_H_
